Plant Reproduction

1. Plant Reproduction
ENOCH B. TACLAN

2. What is Plant Reproduction
 Reproduction is one of the most important characteristic of all
living beings. It is the production of ones own kind.
 It is necessary for the continuation of the species on earth and also to
replace the dead members of the species.
 The process by which living organisms produce their offspring's for the
continuity of the species is called reproduction.
The modes of reproduction vary according to individual species and
available conditions. It may be simply by division of the parent cell as in
unicellular organisms, by fragmentation of the parent body, by formation
of buds and spores, or it may be very elaborate involving development of
male and female reproductive organs (stamens and pistils). Irrespective of
the mode of reproduction, all organisms pass on their hereditary material
to their offspring during the process of reproduction (Reproduction and
Heredity, Biology Module Chapter 18)

3. Plant Reproduction
Asexual Reproduction
No Gametes
Only one parent needed
New organism genetically identical to
parent
Plants and bacteria reproduce this way

4. Asexual Reproduction
 Fission : As in unicellular organisms like bacteria where the content of the
parent cell divides into 2, 4 or 8 daughter cells and accordingly the fission
is known as binary or multiple fission. Each newly formed daughter cell
grows into a new organism.
 Budding : A bud like outgrowth is formed on one side of the parent cell
and soon it separates and grows into a new individual e.g. in yeast.
 Fragmentation : In filamentous algae, an accidental breaking of the
filament into many fragments, each fragment may give rise to a new
filament of the algae by cell division e.g. Spirogyra, green algae.
 Spore formation : In lower plants like bryophytes reproductive units
develop asexually on the parent body. These are called spores. They are
microscopic and covered by protective wall. When they reach the suitable
environment they develop into a new plant body e.g. in bread moulds,
moss, fern.

5. Plant Reproduction
Sexual Reproduction
Male and Female Gametes involved
Two parents are needed
New organism will not be genetically
identical to either of the parent

6. Reproduction in Lower Plants
 Chlamydomonas (A Unicellular Alga)
 Asexual-with the help of zoospores
 Chlamydomonas loses flagella and becomes non-motile.
 Its protoplasm (cytoplasm and nucleus) divides mitotically and
forms 4-8 zoospores.
 The parent cell wall is ruptured and zoospores are released.
 Each zoospore develops a cell wall and grows into an adult
cell.
 The parent cell does not exist, any more.

7. Reproduction in Lower Plants
 Sexual Reproduction
 The cell becomes non-motile by losing its flagella.
 The protoplasm divides mitotically into 2, 4, 8, 16, 32 daughter cells.
 Each daughter cell develops flagella and is released in water by the rupture of
mother cell wall. It acts as a gamete.
 The gamete is morphologically identical in structure but all identical
(Isogamous).
 Gametes released from two different mother cells fuse together.
 The contents of the gametes fuse and form a zygote (diploid). This is the only
diploid stage in the life cycle of Chlamydomonas.
 The zygote develops a thick wall around itself to tide over unfavourable
conditions (zygospores)
 On the return of favourable conditions (temperature, food and water) the
diploid nucleus divides by meiosis and forms four haploid zoospores.
 Each zoospore grows into a new adult Chlamydomonas

9. Vegetative Reproduction
 involves formation of new plantlets from
vegetative (somatic) cell, buds or organs of the
plant.
 It is similar to a sexual reproduciton in that it
also requires only mitotic division, no gametic
fusion and daughter plants are genetic clones
of the parent plant.

10. Spirogyra (A Multicellular Alga)
 Vegetative Reproduction by fragmentation
 The filament breaks into small fragments.
 Each fragment grows into a new filament by cell division
 Sexual Reproduction
 Two filaments come to lie very close to each other.
 Cells of the two filaments form a contact with the help of a tube called the
conjugation tube.
 Cytoplasmic contents of each cell round off to act as a gamete.
 Gamete from one cell (male) passes to the other cell (female) through the
conjugation tube.
 Each filament acts either as male or female.
 The contents of two gametes fuse in the female cell and form a diploid zygote

11.  The zygote develops a thick wall around itself and tides over the
unfavourable period.
 On the return of favourable conditions the diploid nucleus divides by
meiosis into four haploid nuclei. Three of these nuclei degenerate.
 On germination, wall of the zygote ruptures and a small tube like structure,
containing one haploid nucleus comes out.
 The small tube develops into 1 filament by repeated mitotic divisions.

13. Reproduction in Angiosperms
(Flowering plants)
 Angiosperms reproduce both vegetative and sexual methods
 Angiosperms reproduction occurs by fusion of male and female gametes
present in the flower.
 Angiosperms can be classified depending the time they take to complete
life cycle and flowering
 Annuals – Live for one year , produce flowers and seeds within one season
 Biennials - two seasons, first year vegetative state, second year produce
flowers, fruits and seeds
 Perennials – plants which live for several years , one to few years vegetative
stage then after that flowers, fruits and seeds every year
 Monocarpic - plants are those that flower, set seeds and then die

14. Plant Reproduction
The Flower:
The flower is the part of a plant
that is involved in sexual
reproduction

15. Plant Reproduction
 Initiation of flowering
 The young plant grows vigorously and continue to
grow till it attains a definite shape and size with its
vegetative parts (roots, stem, leaves) well developed
 Young or the Juvenile phase
 Reproductive phase or adult phase
 Vegetative shoot apex transforms into a reproductive
or floral apex and starts bearing flowers

16. Plant Reproduction
The Parts of the Flower
Sepals
Petals
Carpel
Stamen

17. Plant Reproduction
Sepal:
Green leaves which protect the
flower when it is a bud
Petals:
Attract insects to the flower

18. Plant Reproduction
 The Stamen:
 Male Part of the flower
 Filament – stalk part of stamen
 Anther – Small bag on top of the filament contains
pollen

19. Plant Reproduction
 Structure of the Carpel:
 Stigma – Pollen grains land here
 Style – Connects stigma to the ovary
 Ovary – Contains ovules
 Ovules – Contain female gametes – eggs
 Pistil - The ovule producing part of a flower

20. Plant Reproduction
Stages in Sexual Reproduction in Plants:
Pollination
Fertilisation and Seed Formation
Seed Dispersal
Germination

21. Plant Reproduction
Pollination: Happens when pollen
from one flower is transferred to
another flower of the same species
Insect Pollination(Entomophily) or
Wind Pollination (Anemophily)

22. Plant Reproduction
TWO TYPES OF POLLINATION
Self pollination – transfer of pollen grains to
stigma of same or another flower of same
plant
Cross pollination – transfer of pollen grains
to stigma of a flower of another plant of the
same species

23. Importance of Pollination
 It results in fertilization and ovule is converted into seed.
 New varieties of plants are formed through new combination
of genes in case of cross pollination.
 During pollination pollen tube produces growth hormones
which convert ovary into fruit.
 Cross pollination is brought about by various external
agencies such as, wind, insects, water, birds and other animals.

24. Plant Reproduction
 Insect Pollination:
 Petals are bright and perfumed.
 Insect rub against Anther and pollen gets stuck to
them
 Insect move to another plant of same species and
pollen sticks to sticky stigma

25. Plant Reproduction
 Wind Pollination:
 The flowers have long anthers which hang outside
the flower.
 Pollen is blown out of the anthers by the wind
 The stigma of a wind-pollinated flower is very large
and feathery – able to catch pollen

26. Plant Reproduction
 Fertilisation and Seed Formation:
 After pollination, pollen tube develops out of the pollen grain
and into the style,
 It then enters the ovule and male gamete travels down to join
with the egg – zygote
 The zygote then becomes the seed.
 The ovary will turn into the fruit

27. Plant Reproduction
Dispersal Of The Seed:
 The major function of the fruit is to scatter the seed
of the plant
 Animal Dispersal
 Wind Dispersal
 Water Dispersal
 Self Dispersal

28. Plant Reproduction
 Animal Dispersal:
 Edible Fruits: Animal eats fruit and eventually passes
the seed in its droppings, if seed falls in right place it
will grow into new plant
 Hooked Fruits: Fruits have tiny hooks on their surface,
sticks to the animals.

29. Plant Reproduction
 Wind Dispersal:
 The wind provides a very effective method of carrying
fruit away from the parent plant
 Dandelion uses parachute
 Sycamore tree uses winged fruits

30. Plant Reproduction
 Water Dispersal:
 The water lily is an example of a plant with
fruits that can float.
 Water currents carry the fruit away, with the
seeds inside

31. Plant Reproduction
 Self Dispersal:
 The gorse plant can scatter its own seed.
 In summer the plant dries out and suddenly bursts.
 The seeds shoot out from the fruit, and may land
some distance from the parent plant

32. Plant Reproduction
 Germination:
 Plumule – Will form shoot of plant
 Radicle – Will become the root of the plant
 Testa – Protects the seed
 Food Store – Provides nourishment for the
young plan

33. Plant Reproduction
 Conditions Necessary For Germination:
 Water
 Oxygen
 Warmth

34. Vegetative Reproduction in
Angiosperms
 Reproduction of new plants from the portion of the
vegetative parts of a plant is very common and is called
vegetative reproduction. Stems, roots, leaves and even buds
are variously modified to suit this requirement. This is called
natural vegetative reproduction.
 Natural Method : In natural methods, a portion of the plant
gets detached from the body of the mother plant and grows
into an independent plant. The parts may be stem, root, leaf
or even flower

35.  The underground modification of stem, like rhizome, (in ginger), tuber
(potato), bulb (onion) are provided with buds which develop into a new
plant and therefore used to carry out vegetative propagation of the plant
in the field. Plants with subaerial modification such as Pistia (offset) and
Chrysanthemum (sucker) are also used for vegetative propagation.
 Similarly, tuberous roots (Asparagus and sweet potato) can also be used
for propagation as these roots have adventitious (form accidentally) buds
which ground into a new plant.
 Sometimes even leaves contribute to propagation of plants leaves of
Bryophyllum that have buds on the margin and these buds grow into small
plantlets. When detached from the mother plant they grow into
independent plants.
 In plants like Agave and Oxalis multicellular bodies called bulbils develop
near the flower. These are called bulbils which when fall on the ground
grow into new plant

36. Vegetative Reproduction in
Angiosperms
 Humans have taken advantage of this natural phenomenon and have
artificially propagated plants vegetatively by using the specialized parts as
by cutting, grafting and layering.
 Cuttings: Many plants like rose, Bougainvillea, Croton, Coleus, money
plants, sugarcane etc. are grown through their stem cuttings. Cuttings of
these plants can be grown even in water where they strike roots and
develop adventitious buds
 Layering: In this method, a lower branch of a plant is bent down and
covered with moist soil leaving the growing tip above the soil. A ring of
bark is removed from the stem before it is bent down. In a few weeks time
when enough roots have developed on the underground portion above
the ringed part, it. is cut off from the parent plant and grown separately as
an independent plant.

37. Vegetative Reproduction in
Angiosperms
 Aerial layering or Goatee : In this method a ring of bark is removed from a
selected branch, and it is covered with moist moss and enclosed in a
polythene sheet when roots appear, the stem is cut below the roots and
planted to form a new plant

38. Vegetative Reproduction in
Angiosperms
 Grafting – The purpose of grafting is to combine one plant's qualities of
flowering or fruiting with the roots of another that offers vigour and
resilience. This is a difficult task and requires lots of skill and practice. In
most cases, trees and shrubs are available to buy already grafted onto a
rootstock.
 In this stock a branch is inserted which is known as scion or graft. This
scion or graft is the stem cutting from the desired plant. Usually the
grafted end of stock and scion fit well with each other and are bound
firmly with tape or rubber-band until their tissues unite and vascular
continuity is established. Grafting is mostly. practised in dicot plants

39. Advantages and Disadvantages of
Vegetative Reproduction
 Advantages
 (a) Rapid means of reproduction and spread.
 (b) Offsprings identical to parent. The desired varieties can
thus be preserved genetically for use.
 (c) Food storage organs allow perennation or survival in
adverse condition
 (d) Improved varieties of ornamental plants and fruit trees can
be multiplied easily.
 (e) Vegetative propagation is a quicker, easier and a less
expensive method of multiplying plants

40.  Disadvantages
 (a) Overcrowding and competition for space unless
separated artificially.
 (b) New varieties cannot be produced by this method
except by mutation.
 (c) Diseases typical of the species are rapidly
transmitted and can decimate a crop

41. Thank you